IBM solar cell trick brings future of green tech into focus

IBM has cooked up a way to squeeze more energy out of a solar cell, using a …

Last week, IBM announced a new approach to lowering the cost of solar power. Though it's a long way from commercialization, the technique is worth taking a close look at because it exploits some of the technology that IBM has developed for cooling CPUs in order to improve solar cell efficiency. IBM's research in this area also fits within the context of wider industry "green technology" efforts, efforts that are already having a real impact in the datacenter.

Squeezing more power out of a solar cell

Photovoltaic technology, which converts light directly into electric current, has been around in one form or another for decades. So far, it has been limited to niche markets for a single reason: photovoltaic cells are expensive because they are generally made via the same high-quality silicon manufacturing processes that produce computer chips. Solar cell makers have tried to overcome this limitation in a variety of way; some look to alternate materials, while others try to boost the efficiency of energy conversion so that a single chip produces more power.

The new work from IBM is a rather interesting variation on this latter option. Instead of boosting the efficiency of the photovoltaic cell itself, the technique, called concentrator photovoltaics, simply focuses more sunlight onto the chip. With more incoming energy, any photovoltaic, regardless of its efficiency, will produce more power. This technology is already in use commercially, but it's limited by the fact that concentrating too much light will raise the temperature of photovoltaic devices to the point where the equipment starts getting damaged.

The new IBM construct focuses approximately 230 watts/cm2 onto a photovoltaic cell, which is the equivalent of 2300 times the intensity of unfiltered sunlight. That's enough to raise standard equipment to 1600°C and precipitate a meltdown. But the team involved in this research crafted their solar cell using technology intended to help cool processors, thereby allowing it to efficiently transport heat away from the photovoltaic cell and keeping it at a perfectly functional 85°C.

IBM uses a liquid metal cooling system based on gallium and indium for efficiently transferring heat away from the photovoltaics an to a standard metal heat sink. The result is a system that can operate at a light intensity that's roughly five times higher than any concentrator photovoltaic system currently in use. The system is a long way from escaping the lab, but it may get a boost if similar cooling systems become mainstream through their use in processors.

The greening of the data center

This is hardly the first time that IBM has demonstrated an interest in solar technology; last October, the company announced it had found a way to allow the use of scrap silicon wafers in the manufacturing of photovoltaic devices. Solar is hardly the only "green tech" area that they're looking at, either, as the press release for the new concentrator technology proudly proclaimed IBM's interest in, "energy efficient technology and services, carbon management, advanced water management, intelligent utility networks and intelligent transportation systems."

This emphasis on sustainable development is becoming widespread within the high-tech community. Google has gone solar at its own facilities while also investing in solar thermal power companies that are aiming for the general grid. A consortium of manufacturers is also working towards producing a climate-saving PC. In short, green is the new color of high-tech.

It's easy to dismiss these green trends as attempts to capitalize on to a feel-good wave of environmentalism for marketing purposes, and there probably is an element of that in some of these efforts. But they can just as easily be explained as a response to a new economic reality, one in which energy costs continue to rise and become a major contributor to the total cost of ownership of IT equipment.

That reality makes green technology appealing for both IT users and manufacturers in two ways. First, energy-efficient equipment becomes a necessity, as it allows users to continue to add computing capacity and manufacturers to both sell the new capacity and to replace the old tech with more efficient products. Second, renewable power sources become more appealing for everyone involved as economies of scale drive down their costs relative to fossil fuels. Given this equation, it's no surprise that so many companies are now jumping on the green bandwagon.